1. Field of the Invention
The present invention relates generally to a wideband wireless communication system. More particularly, the present invention relates to a resource allocating apparatus and method for performing a Push-To-Talk (PTT) service, which is a simplex communication, in a wideband wireless communication system.
2. Description of the Related Art
In a fourth generation (4G) communication system, research has been conducted to provide users with various Quality of Services (QoSs) at a data rate of about 100 Mbps. Specifically, research of the 4G communication system has been conducted into a high rate service support to guarantee mobility and QoS in Broadband Wireless Access (BWA) communication systems such as Local Area Network (LAN) systems and Metropolitan Area Network (MAN) systems. Representative 4G communication systems include Institute of Electrical and Electronics Engineers (IEEE) 802.16 wideband radio communication systems, which standard is hereby incorporated by reference.
The wideband wireless communication system defines a variety of resource allocation methods, which include an Unsolicited Grant Service (UGS) for periodically allocating data resources of a fixed size without a resource allocation request, a real-time Polling Service (rtPS) for periodically allocating resources that allow the resource allocation request, an extended rtPS (ertPS) for periodically allocating data resources of a variable size as requested, a non-real-time Polling Service (nrtPS) for aperiodically allocating resources that can request the resource allocation, and a Best Effect (BE) for requesting the resource allocation through a random access.
For communications in a wideband wireless communication system, it is necessary to efficiently allocate resources using the above mentioned resource allocation methods. For example, for a Push-To-Talk (PTT) service of the simplex communication service, an efficient resource allocation method is needed. The PTT service is the simplex communication service for allowing only one user to speak at one time. The user presses a PTT button to talk. By releasing the pressing of the PTT button to finish the speaking, the user can hear the other party.
FIG. 1 illustrates a conventional PTT service procedure.
Referring to FIG. 1, when an event for a PTT service with a terminal B 170 is generated according to a key manipulation of a user in step 101, a terminal A 150 establishes a session for the PTT service by transmitting and receiving Session Initiation Protocol (SIP) messages to and from the terminal B 170 via a PTT server 160 in step 103.
The PTT server 160 sends a Floor Grant message to the terminal A 150 which commences the PTT service in step 105, and sends a Floor Taken User_A message of the terminal A 150 to the terminal B 170 in step 107. The terminal A 150, which is granted the floor, transmits user's speaking to the PTT server 160 according to a Real-time Transmission Protocol (RTP) in step 109. The PTT server 160 forwards the received speaking of the terminal A 150 to the terminal B 170 according to the RTP in step 111.
Next, when an event for finishing the talking is generated by the key manipulation of the user in step 113, the terminal A 150 sends a Floor Release Message to the PTT server 160 in step 115. Upon receiving the Floor Release message, the PTT server 160 informs the terminal A 150 and the terminal B 170 of a current idle channel by sending a Floor Idle message to them in steps 117 and 119.
When an event for the speaking start is generated by a user's key manipulation in step 121, the terminal B 170 sends a Floor Request message to the PTT server 160 in step 123. The PTT server 160, upon receiving the Floor Request message, sends a Floor Grant message to the terminal B 170 in step 125 and sends a Floor Taken User_B of the terminal B 170 to the terminal A 150 in step 127.
In step 129, the terminal B 170 transmits user's speaking to the PTT server 160 according to the RTP. The PTT server 160 forwards the speaking of the terminal B 170 to the terminal A 150 in step 131.
When a Floor Release event is generated in step 133, the terminal B 170 sends a Floor Release message to the PTT server 160 in step 135. The PTT server 160 sends a message informing of the current idle channel to the terminal A 150 and the terminal B 170 in steps 137 and 139. When the speaking is not requested over a certain time, the terminal A 150 and the terminal B 170 terminate the PTT session in step 141.
As above, the PTT service allows only one user to speak at one time and transmits data of the user's speaking in real time. The PTT service can allocate resources using the UGS, the rtPS, and the ertPS which support the real time service among the above-mentioned resource allocation methods. However, as for the UGS, the resources are allocated to every user of the PTT service. Unnecessarily, the uplink resource is periodically allocated to the user who is not talking. In case of the rtPS, the uplink resource for requesting the resource allocation is unnecessarily allocated on a periodic basis to the user who cannot talk due to the other user's speaking. In case of the ertPS, a Channel Quality Indicator (CQI) channel is fixedly allocated.